Yemen's Houthi fighters have denied reports that warring parties have reached a preliminary agreement on Tuesday to release all prisoners beginning within 20 days.

The Iran-allied Houthis and Yemen's Saudi-backed exile government are trying to reach a peace agreement in talks in Kuwait aimed at ending a year-long war and easing a humanitarian crisis in the Arabian Peninsula's poorest country.

Government sources at U.N.-backed peace talks earlier on Tuesday said an agreement had been struck to release the prisoners.

However, a Houthi delegate, representing the prisoners' committee at the talks, said the session had only considered a proposal, not agreed on it. Naser Baqizqoz said the suggestion was to release half the detainees on either side within 20 days, not all of them.

Yemen's crisis began in September 2014 when the Houthis, who are allied to Yemen's former president Ali Abdullah Saleh, seized the capital Sanaa.

A Saudi-led Arab alliance intervened in March last year, launching a campaign of mostly air strikes against the Houthis and in support of the forces of current Saudi-backed president, Abd-Rabbu Mansour Hadi.

A tentative U.N-backed ceasefire has been in place since last month to give the peace talks in Kuwait a chance at progress. Both sides have regularly accused each other of violations.

Last month, a Houthi delegation presented a plan to the United Nations for a transitional government to oversee a handing over of arms and freeing of political prisoners before elections.

Yemen's government wanted the Houthis and forces loyal to Saleh to hand over weapons and withdraw from cities captured last year before starting any dialogue, a negotiating source told Reuters at the time.